Three that I have had very good luck with are the Shrewd but only on high pressure rounds, like the 5.56, but they do not seem to work very well on the lower pressure rounds like the .458 SOCOM (yes, I have a Shrewd for the .458 and it does little that I can tell).
Another break that seems to me to be more affective than the Shrewd is the Midwest Industries. I have them in 5.56 and .30 cal and they do a heck of a job of keeping the muzzle on target. Both the Shrewd and the MI will clear your table though if you are not careful.
Last, and this one works very well on the low pressure rounds, is the TROMIX four port fish gill break. I recently built a 7 pound .458 SOCOM (with mag and optic) and the TROMIX break really tamed it down considerably. The TROMIX also has the ports angled away from the shooter slightly and the concussion is not near as great on the shooter as it is with the Shrewd and the MI.
Shrewd on a .358 HDH:
Midwest Industries:
.30 cal on left, 5.56 on right, and yes, that is correct.
TROMIX on .458 SOCOM: